The mixing of orthopedic implants and instruments from various manufacturers leads to risks in hospitals.
We can divide implants into two groups, according to their function:
- Temporary implants to support healing after injury or disease, such as implants for internal fixation
- Permanent implants to replace a living part of the body that has become dysfunctional due to injury or disease, such as joint replacements
Implants should be able to support the body’s biochemical function as efficiently as did the living parts before injury or disease, or at least as efficiently as is currently possible. Many of the implants now in use and the special surgical techniques associated with them have evolved through lengthy periods of development. Since the instruments necessary for implantation form an integral part of the surgical techniques themselves, the techniques face the risk of failure if parts from various sources are used or if the instruments and implants do not match.
The belief that the mixing of implants, the manufacturer or the surgical technique presents no risk for the patient, may possibly be due to commercial pressures. At all events, it suggests the absence of a consistent policy of quality assurance. Some of the possible risks and problems associated with the mixing of implants, instruments, and surgical techniques are described below:
At first sight, the use of a combination of 4.5 and 6.5 mm bone screws from different manufacturers would seem acceptable and free from obvious problems. Though it makes no claim to completeness, the list below outlines some of the causes that can lead to serious damage, wear, and malfunction of the implant, and to surgical and functional problems.
- Unsuitable combination of materials: for example, cobalt- chromium or Titanium screws should not be used in combination with stainless steel.
- Nonstandard material: inadequate quality control of the raw material leads to poor overall material quality, corrosion, and metalloids.
- Insufficient mechanical strength: due to manufacturing processes, improper heat treatment, or poor- quality material; leads to screw failure or corrosion.
- The screw head does not fit the hole in the plate: not spherical or wrong diameter.
- The screw’s core diameter does not fit the hole in the plate: this may cause the screw to jam or damage the implant’s surface.
- The pitch of the screw thread does not match that of the tap: the screw jams during insertion or the surgeon may strip the thread.
- The screwdriver does not fit the recess on the screw head: if this prevents the use of the wrong screw or screwdriver, it automatically solves the problem.
- It proves impossible to achieve the maximum angle of about 20⁰ for lag- screw positioning: this may affect the fixation system and prolong surgery.
- The screwdriver does not fit the hexagonal recess on the screw head.
- Unacceptably large deviations in the screw’s core diameter: this may impair the screw’s mechanical strength, cause the screw to jam on insertion, or the surgeon may strip the thread.
The above list deals only with a simple mixture of plates and screws. The situation becomes rather more complex and critical when there is a mixture of several implants and/or instruments.